The judge has until Sunday evening local time to decide whether to press formal charges against Garzon, Interior Minister Jorge Fernandez Diaz told reporters.

The driver, who was hospitalized for two days while under police guard, has been transferred to court, officials said.

The data recorders from the train are still with police.

Questions have focused on the speed at which the train was traveling as it entered a curve in the track near Santiago de Compostela on Wednesday evening.

The crash on the outskirts of the city, which is popular with tourists and Christian pilgrims, shocked the Galician region and the rest of the nation.

Fernandez Diaz told reporters Saturday there are "rational indications" that the accident is the fault of the driver. Pressed on what those are, he declined to provide details.

Galicia regional police chief Jaime Iglesias told reporters Friday that the driver was under police detention because of "a crime."

Asked what crime, he responded: "Well ... in connection to the accident, in connection with his recklessness, in connection with causing the accident."

Identifying the bodies

The crumpled wreckage of the eight cars sent careering onto their sides when the train derailed has been removed from the tracks, but the grim task of identifying the dead continues.

Maria Pardo Rios, a spokeswoman for the Galicia regional supreme court, told CNN late Friday that 75 victims had been identified.

At least 63 of the dead are Spanish, she said. Also among the fatalities are one U.S. citizen, Ana-Maria Cordoba from Arlington, Virginia, and a number of Europeans and Latin Americans.

As they are identified, most of the bodies are being returned to their grieving families, the regional justice department said. DNA testing is to be done on some remains to establish their identity, it said.

Police forensic experts said at a news conference Saturday there are 37 body parts that must still be tested to see whether they belong to bodies that have already been identified, or to others not yet known.

The death toll rose to at least 79 on Sunday morning when another person died, a representative for the regional health department said. About 70 people who were injured in the crash remained in the hospital Sunday, about 22 of them listed in serious condition, the official said.

At least five U.S. citizens were injured, said State Department deputy spokeswoman Marie Harf.

Local newspaper La Voz de Galicia said that a funeral service for the victims will take place Monday evening in the cathedral in Santiago de Compostela.

Going too fast?

Spanish news agency Efe and the national daily El Pais cited sources within the investigation as saying that the driver had said the train was traveling about 190 kilometers per hour (about 120 mph).

Elena Garcia, a spokeswoman for national railway Renfe, did not disclose Friday the speed the train was traveling on an express track, where cars can move as fast as 250 kph. But she said the speed limit for the bend of track where the crash occurred is 80 kph.

Rafael Catala, secretary of state for transport and housing, told Spanish radio network Cadena SER that the "tragedy appears to be linked to the train going too fast," but that the reasons it was going so fast are not yet known.

The express passenger service was nearing the end of a six-hour trip from Madrid to the town of Ferrol in northwest Spain when the crash occurred, the state railway said.

Security footage revealed how, as the train hurtled around a bend, its cars derailed and slammed on their sides into a concrete support structure for a bridge.

Flames burst out of one train car as another car was snapped in half. Rescue crews and fellow passengers pulled bodies through broken windows and pried open doors as stunned survivors looked on.

Maria Vigo, whose home is on the bank above the rail tracks, told CNN how she heard a crash, then the deafening squeal of metal on concrete.

"When I saw the rail car flip into the air, I imagined something just horrible had happened," she said.

She and husband Suso tried to help the injured, taking bed sheets to wrap around the injured and ropes to haul the survivors off the tracks.

Firefighter Miguel Angel Bello said the first four minutes after he arrived on the scene were a desperate race against time.

He and fellow firefighters smashed windows and kicked in doors to pull out the passengers trapped inside as rail cars

went up in flames.

A young girl in the wreckage called out to him.

"She was under wreckage she said she wanted to get out and go home," he said. "But she died."

Survivor: We looked like the walking dead

Stephen Ward, an 18-year-old from Bountiful, Utah, who is in Spain serving on a Mormon religious mission, was one of the lucky ones.

Still patched up and wearing a neck brace, he told CNN's "New Day" show of his ordeal -- and his relief that he made it out alive and without permanent injury.

Ward blacked out when his car slammed on to its side, regaining consciousness only as he was being helped out of the train.

It took him a couple of minutes to grasp that what he was seeing outside was not a dream -- and that people were dead. "They were helping out other people -- there were bodies, there was screaming, there was smoke."

The survivors looked like the walking dead, he said. "I've got staples all over my scalp, I was covered in blood. They've scrubbed most of it off me now, but everyone was just covered in their own blood and occasionally the blood of others. It was gruesome to say the least."

Another victim, speaking from a hospital bed with his arm in a sling, told CNN affiliate Atlas that it seemed like the train was going fast.

"But we didn't know what was the maximum speed, so I thought it was normal," he said, "And suddenly there was a curve, the suitcases fell, and everything went dark. And I hit my head a ton of times, and 10 seconds later I was wedged between seats, and I had people's legs on top of me."

The derailment came on the eve of a public holiday to celebrate a saint's day, when more people than usual may have been traveling in the region. Planned festivities in Santiago de Compostela and across Galicia were canceled after the crash.